The present invention relates generally to light sources, and more particularly to a high efficiency light source in the form of an optical magnetron.
Magnetrons are well known in the art. Magnetrons have long served as highly efficient sources of microwave energy. For example, magnetrons are commonly employed in microwave ovens to generate sufficient microwave energy for heating and cooking various foods. The use of magnetrons is desirable in that they operate with high efficiency, thus avoiding high costs associated with excess power consumption, heat dissipation, etc.
Microwave magnetrons employ a constant magnetic field to produce a rotating electron space charge. The space charge interacts with a plurality of microwave resonant cavities to generate microwave radiation. Heretofore, magnetrons have been generally limited to maximum operating frequencies below about 100 Gigahertz (Ghz). Higher frequency operation previously has not been considered practical for perhaps a variety of reasons. For example, extremely high magnetic fields would be required in order to scale a magnetron to very small dimensions. In addition, there would be considerable difficulty in fabricating very small microwave resonators. Such problems previously have made higher frequency magnetrons improbable and impractical.
In view of the aforementioned shortcomings associated with conventional microwave magnetrons, there exists a strong need for a magnetron which is suitable as a practical matter for operating at frequencies which exceed 100 Gigahertz (i.e., an optical magnetron). For example, there is a strong need in the art for an optical source capable of producing light with higher efficiency as compared to conventional types of light sources (e.g., incandescent, fluorescent, laser, etc.). Such an optical source would have utility in a variety of applications including, but not limited to, optical communications, commercial and industrial lighting, manufacturing, etc.
The present invention provides an optical magnetron suitable for operating at frequencies heretofore not possible with conventional magnetrons. The optical magnetron of the present invention is capable of producing high efficiency, high power electromagnetic energy at frequencies within the infrared and visible light bands, and which may extend beyond into higher frequency bands such as ultraviolet, x-ray, etc. As a result, the optical magnetron of the present invention may serve as a light source in a variety of applications such as long distance optical communications, commercial and industrial lighting, manufacturing, etc.
The optical magnetron of the present invention is advantageous as it does not require extremely high magnetic fields. Rather, the optical magnetron preferably uses a magnetic field of more reasonable strength, and more preferably a magnetic field obtained from permanent magnets. The magnetic field strength determines the radius of rotation of the electron space charge within the interaction region between the cathode and the anode (also referred to herein as the anode-cathode space). The anode includes a plurality of small resonant cavities which are sized according to the desired operating wavelength. A mechanism is provided for constraining the plurality of resonant cavities to operate in what is known as a pi-mode. Specifically, each resonant cavity is constrained to oscillate pi-radians out of phase with the resonant cavities immediately adjacent thereto. An output coupler or coupler array is provided to couple optical radiation away from the resonant cavities in order to deliver useful output power.
The present invention also provides a number of suitable methods for producing such an optical magnetron. Such methods involve the production of a very large number of resonant cavities along a wall of the anode defining the anode-cathode space. The resonant cavities are formed, for example, using photolithographic and/or micromachining techniques commonly used in the production of various semiconductor devices. A given anode may include tens of thousands, hundreds of thousands, or even millions of resonant cavities based on such techniques. By constraining the resonant cavities to oscillate in a pi-mode, it is possible to develop power levels and efficiencies comparable to conventional magnetrons.
According to one aspect of the invention, a magnetron is provided which includes an anode and a cathode separated by an anode-cathode space with electrical contacts for applying a voltage between the anode and the cathode for establishing an electric field across the anode-cathode space with at least one magnet arranged to provide a magnetic field within the anode-cathode space. The anode includes a plurality of wedges arranged side by side to form a hollow-shaped cylinder with each of the wedges comprising a first recess which defines in part a resonant cavity having an opening exposed to the anode-cathode space.
According to another aspect of the invention, a magnetron is provided comprising an anode and a cathode separated by an anode-cathode space with electrical contacts for applying voltage between the anode and the cathode for establishing an electric field across the anode-cathode space; and at least one magnet arranged to provide a magnetic field within the anode-cathode space generally normal to the electric field. The anode comprises a plurality of washer-shaped layers stacked atop each other to form a hollow-shaped cylinder having the anode-cathode space therein and each of the plurality of layers includes a plurality of recesses along an inner diameter which are aligned with recesses of the others of the plurality of layers to define a plurality of resonant cavities along an axis of the cylinder each having an opening to the anode-cathode space.
According to another aspect of the invention, a magnetron is provided which includes an anode and a cathode separated by an anode-cathode space; electrical contacts for applying a voltage between the anode and the cathode and establishing an electric field across the anode-cathode space with at least one magnet arranged to provide a magnetic field within the anode-cathode space generally normal to the electric field; a plurality of resonant cavities each having an opening along a surface of the anode which defines the anode-cathode space, whereby electrons emitted from the cathode are influenced by the electric and magnetic fields to follow a path through the anode-cathode space and pass in close proximity to the openings of the resonant cavities to create a resonant field in the resonant cavities; and a common resonator around an outer circumference of the anode to which at least some of the plurality of resonant cavities are coupled via coupling ports to induce pi-mode operation, wherein at least some of the coupling ports introduce an additional xc2xdxcex delay relative to others of the coupling ports, where xcex is an operating wavelength of the magnetron.
According to another aspect of the invention, a method of making an anode for a magnetron. The method includes arranging a plurality of wedges arranged side by side to form a hollow-shaped cylinder having an anode-cathode space located therein, and forming in each of the wedges a first recess which defines at least in part a resonant cavity having an opening exposed to the anode-cathode space. The method also includes forming a plurality of washer- shaped layers atop each other to form a hollow-shaped cylinder having an anode- cathode space located therein, and forming in each of the plurality of layers a plurality of recesses along an inner diameter which are aligned with recesses of the others of the plurality of layers to define a plurality of resonant cavities along an axis of the cylinder each having an opening to the anode-cathode space.
To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.